<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>03JS数据类型</title>
</head>
<body>
<script>
    //JS数据类型=原始类型+引用类型
    //原始类型：number string boolean null undefined
    var a = 1;
    var b = 9.9;
    console.log(a,typeof a,b,typeof b);
    var c = '你';
    var d = '你好';
    console.log(c,typeof c,d,typeof d);
    var e = true;
    var f = false;
    console.log(e,typeof e,f,typeof f);
    //声明了变量但未赋值，会得到undefined，未定义型
    var g;
    console.log(g,typeof g)

    //引用类型 Object Number String Boolean Array...
    //1)自定义JS对象
    let obj = {
        name:'张三',
        age:18
    };
    console.log(obj,typeof obj); //{name:'张三',age:18} 'object'
    console.log(obj.name,obj.age); //张三 18

    obj.age = 19;
    console.log(obj); //{name:'张三',age:19}

    obj.like = '吃火锅';
    console.log(obj); //{name: '张三', age: 19, like: '吃火锅'}
    console.log(obj.like); //'吃火锅'
    console.log(obj.play); //undefined 访问对象不存在的属性会得到undefined

    //JS数组
    let arr = ['张三','李四','王五',1,2.3,false];
    console.log(arr,typeof arr);
    console.log(arr[0]);
    console.log(arr[5]);
    console.log(arr[99]); //undefined 访问数组不存在的下标，会得到undefined
</script>
</body>
</html>